MECO(TM) Wireless Home Doors Windows Security Entry Alarm System - EASY to install FREE BATTIRES!! (Pack of 2) Easy to install--just peel and stick Magnetic sensor switch detects entry protecting your home or office Operated by 3pcs of. 5VLR44 / AG 13 button cell ( included ) Size: 6.2cm x 3.2cm x 2cm 2 pieces